1. Field of the Invention
The present invention relates to a spinning machine such as a ring fine spinning frame or a ring twisting machine having driving motors for driving respective spindles independently. In particular, the present invention relates to stopping and restarting such a spinning machine for use when a yarn breakage occurs.
2. Description of Related Art
Known in a prior art is a ring fine spinning frame wherein a plurality of spindles for winding yarn are independently connected to respective driving motors. In the fine spinning frame having such an independent spindle driving system, all of the spindles in the fine spinning frame are usually subjected to a simultaneous rotating movement by respective driving motors. On the other hand, switches to selectively stop and restart the drive motors are also independently provided for the respective spindles. Thus, upon an occurrence of a yarn breakage in a spindle, a switch of the corresponding spindle is turned OFF by an operator, so that a drive motor of the corresponding spindle is stopped in order to allow the operator to execute a piecing operation on the broken yarn. After the execution of the piecing, the corresponding switch is turned ON by the operator, which allows the corresponding spindle to be restarted. See, for example, Japanese Unexamined Patent Publication (Kokai) No. 6-57549.
As another related art, Japanese Unexamined Patent Publication (Kokai) No. 2-160934 discloses a fine spinning frame having an independent spindle driving system including independent driving motors for respective spindles, wherein each of the spindles is provided with a stationary braking device for preventing the spindle from being subjected to a torsional force, which otherwise causes the spindle to be rotated in the reverse direction. However, this prior art is not related to the independent stopping of a spindle where a yarn breakage is occurred.
FIG. 32 shows, schematically, a spindle to spindle based driving system in the prior art, where spindles SP are provided, independently, with electric driving motors which are grouped. M1 to M6 are driving motors in one of such groups. In other words, each group includes six motors. Control circuits S1 to S6 are provided for independent stop/restart operation of the driving motors M1 to M6 in the group. These control circuits S1 to S6 for the driving motors M1 to M6 in each group are combined as a single control circuit board S0. The driving motors are, generally, driven by a three phase alternating current, while a direct current is employed for obtaining a braking operation for stopping the driving motors. Thus, the control circuit boards between the groups are connected to an alternating current source AC via connectors X and alternating current lines L1 and are connected to a direct current source DC via connectors X and direct current lines L2. Furthermore, switches SW1 to SW6 are provided for the respective spindles and the control circuits S1 to S6 are constructed by sequential circuits including relays with contacts. The relays are operated by switches SW1 to SW6 in such a manner that the connection of the electric motors to the alternating current source causes the electric motors to be disconnected from the direct current source while the connection of the electric motors to the direct current source causes the electric motors to be disconnected from the alternating current source.
In the prior art as explained above, the control circuits S1 to S6 corresponding to the spindle of a predetermined number in a group are combined to a single circuit board S0. However, in a fine spinning frame, the total number of the spindle may be up to several hundred, which causes the total number of the control circuit board S0 to be correspondingly increased. Furthermore, as explained above with reference to FIG. 32, each of the control circuit board S0 is connected to a total of five lines, three three-phase alternating current lines L1 and the two direct current lines L2. As a result, a total number of the connecting points constructed by the connectors X is highly increased, which results in an increase in the chance of occurrence of electrically imperfect connection, thereby reducing the reliability of an operation of the textile machine, such as a reduced reliability in the braking operation. Furthermore, a direct current is employed for executing the braking function, which makes it necessary to provide, in addition to the alternating electric current source AC, the direct electric current source DC. In addition, each of the spindles must be provided with a control sequence circuit for obtaining a reliable switching operation between the alternating current and the direct current, which increased the production cost of the control circuit S0, i.e., the cost of production of the spinning machine.